A semitrailer is not always parked on even ground, and therefore the loads carried by the two legs of a landing gear are not always equal, and the two legs of the landing gear are not always extending in a perfect parallel alignment. Also, when a loaded trailer is raised on its landing gear, the leg on the far side of the crank lags behind the leg on the near side because of the torsional deflection in the cross shaft. It is believed that this torsional deflection in the cross shaft together with uneven parking surfaces contribute to cause an unbalance in the loads carried by the two legs of a landing gear and a deflection in the frame supporting the landing gear to the trailer.
It is believed that when the legs of a landing gear do not extend in a perfect parallel alignment, an axial tension or a compression stress is generated in the cross shaft, causing gear friction inside the telescoping mechanisms of the legs. In these cases, a larger than normal torque is required to raise or to lower the telescopic legs of the landing gear. It is believed that these large torques have been the major cause of failure of cross shafts on landing gears.
Another contributing factor to explain the failures of cross shafts on the landing gears of semitrailers is believe to be directly related to the handling of trailers. Generally, a highway trailer belongs to a pool of trailers, and is often hauled by several trucks during a same week. A trailer is normally dropped off by one truck at a depot, for unloading and reloading, and picked up later by another truck for delivery to a new destination. A trailer is also often hauled along one segment of a delivery route by one truck and along a next segment by another truck.
The fifth wheels of tractor trucks are not all at the same height, and it is common for a truck operator to try to hitch a trailer that sits too low for the fifth wheel of his/her truck. When the trailer fails to reach the fifth wheel, the truck moves ahead causing the trailer to slide down on the rails of the truck and to fall back on its landing gear. The leg on the crank side of the landing gear is locked in place by the gearing system of the crank. However, the leg on the far side of the crank, that is the passenger-side leg, is held in place by the stiffness of the cross shaft. Again, if the ground is uneven and higher under the passenger-side leg of the landing gear, the jerk applied to this leg is transmitted directly to the cross shaft, often breaking the cross shaft.
The cross shaft between the legs of a landing gear of the prior art is made of a continuous cylindrical pipe, and therefore, one of the legs of the landing gear must be removed to replace a broken cross shaft. The replacement of a cross shaft represents substantial repair expenses, a loss of revenue for the truck operator, a loss of productivity for the trailer and a missed delivery schedule for the recipients of the goods contained in the trailer.
Examples of landing gears having continuous cylindrical cross shafts are illustrated and described in the following documents:    U.S. Pat. No. 2,232,187 issued to F. M. Reid on Feb. 18, 1942;    U.S. Pat. No. 2,885,220 issued to T. B. Dalton on May 5, 1959;    U.S. Pat. No. 3,201,086 issued to T. B. Dalton on Aug. 17, 1965;    U.S. Pat. No. 3,518,890 issued to B. Eastman on Jul. 7, 1970;    U.S. Pat. No. 3,596,877 issued to B. Eastman on Aug. 3, 1971;    U.S. Pat. No. 3,632,086 issued to E. Mai on Jan. 4, 1972;    U.S. Pat. No. 3,861,648 issued to J. J. Glassmeyer on Jan. 21, 1975;    U.S. Pat. No. 3,880,403 issued to J. J. Glassmeyer on Apr. 29, 1975;    U.S. Pat. No. 4,004,830 issued to J. T. Belke on Jan. 25, 1977;    U.S. Pat. No. 4,205,824 issued to E. Mai on Jun. 3, 1980;    U.S. Pat. No. 4,402,526 issued to L. C. Huetsch on Sep. 6, 1983;    U.S. Pat. No. 5,538,225 issued to E. VanDenberg on Jul. 23, 1996.
Because of all the expenses and inconveniences associated to the replacement of a broken cross shaft, it is believed that a need exists for a cross shaft for a landing gear that can resist uneven and shock loads and that can be installed quickly without having to remove one leg of the landing gear.